Grid-type liquid delay line



Margh I1, 1958 1, PAGE 2,826,745-

I GRID TYPE LIQUID DELAY LINE Filed. Aug. 5, 1946 2 Sheets-Sheet 1SWITCH 6 B\ I INDICATOR CANCELLER RECEIVER DELAY LINE TRANSMITTERAMPLIFIER 1/ I IIIIIIIIIIIIIIIII 11/11/1111! mvmmx. IRVING H. PAGE ATTORNEY March 11, 1958 I. H. PAGE 2,826,745

v GRID-TYPE LIQQID DELA l LINE Filed Aug. 5, 1946 r 4 2 Sheets-Sheet 2mmvrox. IRVING H. PAGE A TTORNEY t been widely employed, their'use 'hasbeen limited in general to object locating-systemintendedfordete'ctingmov- Ice 2,826,745

157 Patented Mar. 11,1958

United tates atent 121 ing objects at relativelyshort distances. Y Whereobjects at =1ong distance's were to" be de'tecte'dthe n'eces'sary' delayre- GRID-TYPE LIQUID'DELAYILINE 5 quired has exceeded the maximumfeasibledelayiobtainn able-"from a delay line of reasonablesize."This'will be Irving Page Washmgton re'adily' apparent when it' isconsidered'that the delay is 'Applicafion Augustl 5,*1946,"Serial No.688,413 directly proportional to the "length of the path over. which r:Athe com ressionalwave must travel.

' 4 Claims" (CL 333?) ll) i An ol ject of thepresent invention is'to'pro'vide'ra new 1(Granteda1uder Titler35,ULSiGode (1952); serrateand1 imPreveddelayttype-trainsmiesiofi and re'pa ticularly a 'del'ay'typetransmission linecapable of providing a very long delay} ascompa'red with the'size'ofithe L h Invention relatesrtoelecmcabfianmlseonelmese i Other objects and 'advantages oflthe pres'ent'invention ene partleularlyeteedelay typetransmlsswnlmes- "will be apparentlfrom thefol owing"detailed=-description g m? InstanceslflwhlchelectricaldelayltYPe taken. in conjunction witlrthe drawings;wherein:

't l e areleqmred'; Fonexampleiwertain Fig. 1 isa'schematiddiagram-illustrativeofaradioradioobwctlocatmgsystemsdesignedtodistinguishmov- -f bj t l ti jst m i r e ytransmismg targets from fixed targetsnutilizedelayetypetransmisslon lines; to .permit comparisonh of-iconseoutiveetarget Fig 2is ft ld l y. type transmission n smce-echo-Pulses afefetumedfmmtbothlfixed :rline constructedinaccordance with onee'mbbdim'ent of andmov1ngobjects,.-certain moving objects maybe lost in this i i torobscured-by'ground: clutter and? echoes returnedfrom 3 i an' e larg'ed ltransverse; Section-a1 p rstationary objects. In-objectlocatingsystemsdesigned to b i ll l g11 1i i3;;.3 6f Fi 2;

, obv1ate..th1s-d1flicu1ty, fixed iobjectsi are manifested by 4 isaplanflecfion'bf a adaTtype.uransmissionfine W F Pulses having aconstant'amphtude, Whfireasimovmg constructed in accordance with asecondwmbodiment of .rob ectseare i manifested by video pulsesirhaving acyclical his i ention;tand evarletren in rampli'flldev With/find jrepresented Fig. Sis a.transversm 'sectional-view taken" substantially1; by. constant amplitude-video pulses; there is; no' difference alongthe line 5 5' f :4

1 -there is a difierence in amplitude betweensuccessivevideo y object'locating l ye iu t m i r I i vid d "P p n moving j s, y comparing whichis"connectedi through suitable means-to atransmity ewpesueeesstvefvldeepulses w toward receive switch 2,-an'd thereb toasuitable'rlirectional'radithed1fierenee amphtude-between them, a i -handevice: 3,:such as' a parabolic ahtennafiTransmitres dual pulse1sobtained f r moving obieetsbntineffel' "Lrreceive switch 2 serves toconneet'the-transmitter ltdthe pl lnifmeiuchsystemiifllef compaljisoflof @antenna' 3 during'pulse transmission,""but'duringithe in- 'P S= 111afixed obiectcancellel' Whwhcon' terval between exploratory pulsesithe"transmit-receive "5191s ametwolkadapted to Obtain a-l'esidualisignal :zzswitch 2.disconnects 'the transmitter'l 'from the antennairpulsesfappliedsimultaneouslyithereto-BY applying this "tion of echopulses. *The output of there'ceiver 4 iseap- -I'6Sldl1a1 signal to asuitable indicator,isucl1 as a cathode I plied to a delay line sandSimultaneously to -fi 'd object Y r isievident'rthfi moving Objects yWill-be :canceller which may beconnectedf to the delay line" 5 thereolhI11 f' compare any Successive through an amplifier 7;"so that thealternation resultant xpulses, however, it is necessary 'to store or todelay the 451mm 'thetpulsegpassing :thmughmthe delayelhle may} be:firstvideo pulsefor a periodof time equal to the interval 1compensated, Pulses from agiven" object may thus herebetween the twopulses. Inpractice, this interval" is equal versed i l i in'passingthrough thedelay' .linS' but tto theupredetermined intervalbetween-successive explorabe f the same-amplitude athe'pulseapplieddirectly-1o oryp ses.

v v the fixed object canceller'from" the receiver. 'Theou'tput Onemeansefrrevldmgthe a delay e rof the fixed object cancellerfi is-applied toan indicator use-of a delaytype transmission line. Such a line may 8,such as acathode ray tube. As-successive pulses from consist ofaitransmitting medium confinedbetween two ,fixed j have aconstantramplimde, these pulsescan. P F crystals- Signal to delayed P'cel in the fixed objectcanceller 6 and no residual. output -:pl1ed toone of the crystals (the transmitting'crystal) call is obtainedtherefrom. Successive echoes fromtlmovi'ng rung ltteieseillate inaccordance With the well-knelgvnplezeobjects on the other .hand,vary' inamplitude antleheiiee electridphenomenen. The mechanical OSClllatlOnSPI'O- comparing a delayed pulse anjund elayed ulsed -duced aretransferred to the'transm g medium fixed object canceller'6, a residualoutputeislobtained e p e n Wave, Whwh' travelsfhrenghthe transmfl; whichis then applied. to indicator 8 to provide aniudica- 'itmg medlum to theother (recelving) crystal, where it .5 f moving objects,

Lstresses the said receiving crystal to induce an electric It will beapparent fromthe foregoing that it is essential #ehargethereon- Thesignal induced the receiving that the pulse to be delayed passthroughthefdelayL-line 'v' efthe same general character as r gin withoutdistortionand preferably with minimumattenua- Signal pp to'thetransmitting y bufis delayed tion. The delay also must be constant. Inaccordance "for a period oftime equal to the time required for the withthe present invention, a delayline' has 'beenprovide d compressionalwave to travel through the transmitting mewhich, while meetingtheserequ'irernents, also enables-a dium. Since the delayed pulse willnot coincide with the very long delay without requiring the use :of .anunduly 1 'succeedingmndelayed pulse unless the'interval'between largedelay line. i successive exploratory pulses is precisely the same as theReferring 'now to' Figs. 2 and 3 in 'Whichoneembddiinterval provided bythe delay line, means are usually pro- -mentof this invention isillustrated, it twillrbe. seeiilthat'a wided whereby the': intervalbetween successive exploratory liquid delay line is there showncomprising an elongated, pulses is predetermined 'bylthe delay line.rectangular tank. 10, which is preferably made of steel; or

E"=Whi1eLheretoforexsuch.ldelay'linesas describednhave other materialhaving'high dimensional 'st'abilityf'Two asse /4s similar, spaced,parallel walls 11 and 12, respectively, are disposed within the tank,and the left end of the wall 11 is in contact with the left end wall 13of the tank while the right end of the wall 11 is spaced from theopposite end wall 14 of the tank 11. Conversely, the wall 12 has itsright end attached-to the end wall 14 of the tank 11 while its left endis spaced from the end wall 13 of the tank.

The tank 10 is thus divided into three parallel, rectangularcross-section channels of equal width, length and depth. In the upperleft end wall 13 of the tank 1%, as viewed in Fig. 2, is mounted acoaxial cable fitting 15, the fittmg extending transversely through thewall of the tank and having secured to its inner end an insulatingsleeve 16 and a substantially cylindrical contact member 17 which isconnected to the central conductor of the coaxial fitting. Apiezoelectric crystal 18 is suitably secured to the circular end of thecrystal holder assembly, as by cementing, a circular disc shape as moreclearly The crystal 18 is the input or transmitting crystal. A receivingor output crystal 20 of similar characteristics to the crystal 18 issecured to a crystal holder, designated generally at 21, substantiallyidentical to the crystal holder for the crystal 18, and mounted in thelower right portion of the end wall 14 of the tank It), as viewed inFig. 2. The tank 10 is filled with a transmitting medium 22 whichprovides suitable band width and hence good signal fidelity. It has beenfound that the acoustic impedance (product of the velocity of soundthrough the medium and the density of the medium) of the transmittingmedium should be substantially equal or matched to the acousticimpedance of the crystals and that mercury satisfies this requirement.

From the foregoing it will be apparent that a compressional Waveproduced by vibration of the crystal 18 will travel to the right, asviewed in Fig. 2, through the mercury. In order to reflect this waveback and along the central channel of the tank 10, to a right angle,corner reflector 23 is provided and, as shown in Fig.. 2, is so mountedin the tank 2 that its apex touches the end wall 14 while its sidesextend respectively to the wall 10 and the wall 12, the axis of thereflector being aligned with the intermediate wall 11. A similarreflector 24 is mounted at the opposite end of the tank 13 between thewall 11 and the lower sidewall of the tank 10, as viewed in Fig. 2, andhas its apex touching the end wall 13, the axis of the reflector beingaligned with the axis of the intermediate wall 12. Thus, a compressionalwave originating at the crystal 18 is caused to travel to the rightuntil it strikes the reflector 23, is then reflected to the left untilit strikes the reflector 24 and finally reflected again to the rightuntil it reaches the crystal 20 producing a charge thereon as a resultof the piezoelectric effect. The signal induced on the receivingcrystal20 is of the same general character as the original signalapplied to the transmitting crystal 18, but is delayed for -a the delayline shown in Figs. 2 and 3 involves no sacrifice in fidelity and thatthe attenuation is no greater than would be incurred in using astraight, that is, a non-reflecting, delay line having an equivalentlength. On the other hand, the delay line may be made substantially morecompact than the straight type delay line and it will be readilyapparent that additional channels may be added as required. Therectangular channels are not only easier to fabricate but also have lesstendency to produce in the reflected waves elliptical polarization, suchas occurs with tubular channels. It has been found in practice that itis desirable to employ odd numbers of channels in order to keep thecrystals apart, that is, to avoid mounting the crystals in the same endplate. In use a suitable cover plate (not shown) would, of course, beemployed to prevent loss of mercury.

Referring now to Figs. 4 and 5, it will be seen that a on as a result ofthe piezoelectric effect.

4 somewhat more complex type of delay line is there illustrated. Thisdelay line, however, provides a substantially longer delay in the samespace and at the same time eliminates transverse modes of vibration thusproviding a higher fidelity output without requiring that the channelsbe precisely held to a certain size. In accordance with this embodimentof the present invention, a heavy rectangular block 30, which is formedof a material having high dimensional stability such as steel, is milledout to provide a plurality of generally diagonal, rectangular crosssection, and thus channels crossing at right angles, forming in effeet agrid. Thus, a signal applied to a transmitting medium 31 filling thechannels forming the grid from a piezoelectric crystal 32 mounted in asuitable coaxial fitting designated generally at 33 and disposed at onecorner of the block 30 adjacent an end of a channel, the fitting beingsimilar to the fittings hereinbefore described, travels through a firstchannel 34 until it reaches the right sidewall 35 of the block. At thispoint a reflector plate 36 is mounted and is preferably made adjustableto correct for slight errors in milling. The reflector plate 36 causesthe compressional wave to be reflected into a short channel 37 similarto the channel 34 and extending to the left at right angles therefrom.Adjacent the left end of the channel 37 a second reflector plate 40 ismounted in the upper end wall 41 of thetank 30. The reflector plate 40reflects the compressional wave into a channel 42 extending at rightangles to the channel 37 and parallel to the channel 34. A thirdreflector plate 43 is mounted in a left end wall 44 of the block 30adjacent the end of the channel 42 and serves to reflect thecompressional wave at right angles into a channel 45 extending at rightangles to the channel 42 and parallel to the channel 37. A fourthreflector plate 46 is mounted in the lower end wall 47 of'the block 30adjacent the end of the channel 45 and serves to reflect thecompressional wave into a channel 48 connected at right angles to thisend of the channel 45.

In the same manner channels 50, 51, and 52 are formed in the block,being connected seriatim, and extending consecutively at right angles toeach other. Reflector plates 53, 54, and 55, respectively, are mountedin the side walls of the block 30 so as to reflect a compressional wavefrom the channel 48 into the channel 50, then into the channel 51, andfinally into channel 52. At the lower right corner of the block 30 asviewed in Fig. 4, and at the lower end of the channel 52 is mounted asecond crystal 56, this crystal serving as a pick-up or receivingcrystal and being suitably connected to .a coaxial fitting 57. In use asuitable cover plate (not shown) would, of course, be-employed toprevent loss of mercury.

When a compressional wave is produced in the transmitting medium 31filling the several channels described by applying a signal to thetransmitting crystal 32, the wave will travel through the severalchannels and eventually reach the pick-up crystal 56, inducing a chargethere- The signal induced on the receiving or pick-up crystal 56 will bedelayed a period of time proportional to the time required for thecompressional wave to travel through the transmitting medium 31. It hasbeen found that the grid design shown in Fig. 4 provides essentiallyfree space transmission and has the advantage over the type of delayline shown in Figs. 2 and 3 that the reliquirement that the channels beof a certain predetermined size with respect to the frequency to betransmitted in order to obtain fidelity is considerably less rigid.Dispersion of the compressional wave is held to a minimum and spuriousmodes eliminated at 'the junction points. Accordingly, the wave reachingthe receiving crystal 56 is essentially of the same form as that appliedfrom the transmitting crystal 32, that is to say, this delay lineprovides a high fidelity transmis- 8101].

While but two embodiments of the present invention have been shown anddescribed, it will be understood that many changes and modifications maybe made therein without departing from the spirit or scope of thepresent invention, which is limited only by the appended claims.

The invention shown and described herein may be manufactured and used byor for the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A delay line comprising a substantially rectangular container, aplurality of generally diagonal channels each of equal and uniformrectangular cross-section extending through said container and beingconsecutively connected at their ends at right angles to form a grid, atransmitting medium in said channels, a first electricalmechanical meansmounted in said container at one terminus of said grid, a secondelectrical-mechanical means mounted in said container at the otherterminus of said grid, and reflector means at the connected end of saidchannels for reflecting a compressional wave produced by said firstelectrical-mechanical means to said second electrical-mechanical meansalong said channels.

2. A delay line comprising a substantially rectangular container, aplurality of generally diagonal channels each of equal and uniformrectangular cross section extending through said container and beingconsecutively connected at substantially right angles at their ends toform a grid of crisscrossed channels, a transmitting medium filling saidchannels, said channels forming a delay path, a firstelectrical-mechanical transducer means mounted in said container at oneterminus of said delay path and operable in response to an appliedelectrical signal to produce a compressional wave in said transmittingmedium, a second electrical-mechanical transducer means mounted in saidcontainer at the other terminus of said delay path and operable inresponse to an applied compressional wave to produce an electricalsignal, and reflector means located at the connected ends of saidchannels for reflecting a compressional wave produced by said firstelectrical-mechanical transducer means along said delay path to saidsecond electrical-mechanical transducer means.

3. A delay line comprising a container, a plurality of channels formedby said container consecutively connected at the ends of said channelsat right angles to each other to form a grid having two terminuses, atransmitting medium filling said chambers to form a delay path betweensaid terminuses, a first electrical mechanical means mounted at the oneterminus of said grid, a second electrical mechanical means mounted insaid container at the other terminus of said grid, reflector means ateach of the connecting ends of said channels for refleeting acompressional wave produced by the first electrical mechanical means tosaid second electrical mechanical means along said channels.

4. A delay line comprising a substantially rectangular container, aplurality of diagonal intersecting channels extending through saidcontainer to form a grid of criss-crossed channels, said grid having twoterminuses and said channels being connected at right angles at theirends, a liquid transmitting medium filling said channels to form a delaypath between the two said terminuses, a first electrical mechanicaltransducer mounted in one terminus of said container and operable inresponse to an applied electrical signal to produce a compressional wavein said transmitting medium, a second electrical mechanical transducermounted in said container at the other terminus of the grid and operablein response to an applied compressional wave from the first transducerto produce an electrical signal, and reflector means located at theconnected ends of said channels for reflecting the compressional waveproduced by said first electrical mechanical transducer along said delaypath to said second electrical mechanical transducer.

References Cited in the file of this patent UNITED STATES PATENTS2,155,659 Jeflree Apr. 25, 1939 2,263,902 Percival Nov. 25, 19412,421,026 Hall et al. May 27, 1947 2,427,348 Bond et al. Sept. 16, 19472,505,364 McSkimin Apr. 25, 1950

